Echo cancellation is a process of removing echo from a voice communication in order to improve voice quality on a voice communication such as a conventional telephone call or a mobile phone call. Sources of echo may comprise, for example, acoustic echo and/or hybrid echo. Acoustic echo arises when audio or sound from a speaker is picked up by a microphone. The speaker may be, for example, an earpiece of a telephone handset and the microphone may be a microphone in the very same handset. The acoustic echo may exist in any communications scenario where there is a speaker and a microphone, especially during a hands-free operation. Hybrid echo may be generated by the public switched telephone network (PSTN) through a reflection of electrical energy by a device called a hybrid. Most telephone local loops are two-wire circuits while transmission facilities are four-wire-circuits.
The echo cancellation process may sometimes result in what is referred to as residual echo. The residual echo is an echo that is not cancelled by the echo cancellation process. This may occur as a result of a deficient length of an adaptive filter, a mismatch between a true and an estimated echo path, and/or nonlinear signal components, for example. To eliminate the residual echo, a residual echo suppression process may be used. The residual echo suppression process may employ a non-linear processor (NLP) function, for example.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.